Air filter housing with guides for air filter units

ABSTRACT

An air filter housing ( 1 ) has at least one filter chamber ( 2, 3 ) with an inlet end and an outlet end for air passing through a filter unit (F) disposed in the filter chamber, an access opening ( 4, 5 ) arranged in a sidewall of the filter chamber for the introduction of an air filter unit into and removal thereof out of the filter chamber, and a clamping device ( 8 ) for pressing an air filter unit disposed in the filter chamber against an end wall of the filter chamber in the inlet end thereof. The housing has a guide ( 19, 20, 21 - 24 ) for guiding an air filter unit (F) during introduction into and removal out of the filter chamber ( 2 ).

TECHNICAL FIELD

The present invention relates to an air filter housing having at leastone filter chamber with an inlet end and an outlet end for air passingthrough a filter unit disposed in said filter chamber, an access openingarranged in a sidewall of said filter chamber for the introduction of anair filter unit into and removal thereof out of said filter chamber, anda clamping device for pressing an air filter unit disposed in the filterchamber against an end wall of said filter chamber in the inlet endthereof. The invention also relates to an air filter unit adapted to beused in such an air filter housing.

BACKGROUND OF THE INVENTION

Filter housings according to the introduction are known from filteringdevices for certain laboratories or the like in which there is a riskthat the ambient air will be contaminated. In order to prevent air fromsuch environment to leak out, such laboratories often are set undersub-pressure. The function of the filter is to capture all infectiousparticles or other contaminations, such as bugs or other air carriedinfectious organisms, in the circulated air. There is thus a risk thatthe filter unit will contain dangerous contaminations after thefiltering device has been in operation. Before changing a filter unit itmust therefore be ensured that the possible contaminations capturedtherein no longer are dangerous to human beings. This is done by lettinga decontamination gas pass through the filter unit in order to kill allbacteria or other infectious or contagious organisms or the like. It istherefore essential that the air or gas pass through the filter unit andnot outside thereof. In order to ensure that air to be filtered ordecontamination gas pass only through the air filter unit, sealingelements are arranged between the respective end of the filter unit andan end wall of the filter chamber and the clamping device, respectively.

However, the persons changing taken out a used filter unit andsubstituting the removed air filter unit by a fresh one are oftendressed in uncomfortable protective clothing so that their movements arerather awkward and clumsy. There is therefore a great risk that the airfilter unit or the sealing elements thereof be damaged duringintroduction of the unit into a filter chamber, especially if the airflow is vertical in the filter housing.

An objective of the present invention is to reduce the risk for damagingan air filter unit during introduction thereof into a filter chamber.Another objective is to facilitate introduction of and change of airfilter units in a filter chamber in an air filter housing.

SUMMARY OF THE INVENTION

These objectives are accomplished by an air filter housing having atleast one filter chamber with an inlet end and an outlet end for airpassing through a filter unit disposed in said filter chamber, an accessopening arranged in a sidewall of said filter chamber for theintroduction of an air filter unit into and removal thereof out of saidfilter chamber, and a clamping device for pressing an air filter unitdisposed in the filter chamber against an end wall of said filterchamber in the inlet end thereof, characterised by a guide for guidingan air filter unit during introduction into and removal out of saidfilter chamber.

In a preferred embodiment said guide also guides the movement of the airfilter unit within a filter chamber and holds an air filter unitdistanced from the end walls of said filter chamber during introductioninto and removal out of said filter chamber. Said guide can include arail in two opposite walls of said filter chamber, said rails beingextended in a transverse direction relative to the flow direction of theair in the filter housing and to a plane through the access opening tothe filter chamber. Preferably, said rails are movable in the flowdirection of the air in the filter housing and biased to a firstposition by a spring force being stronger than the gravitational forceof an air filter unit being guided and held in the rails, said airfilter unit being distanced from the end walls of said filter chamber insaid first position of said rails.

In a second embodiment the flow direction of the air in the housing isvertical and the rails are held in a first position by a flexibleelement affixed to the clamping device, said air filter unit beingdistanced from the end walls of said filter chamber in said firstposition of said rails.

The invention also relates to an air filter unit adapted to be used inan air filter housing as described above, characterised in that it hasmeans for co-operation with guide means in the air filter housing.

In a preferred embodiment the air filter unit has bars on the outside ofopposite side walls slidable in rails in side walls in said air filterhousing. Advantageously, the ends of said bars are bevelled.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall now be described with reference to the enclosedFigures, of which;

FIG. 1 schematically discloses a perspective view of an air filterhousing according to a preferred embodiment of the invention with thedoors for the access openings to the two filter chambers being opened,

FIG. 2 schematically discloses a partly sectional side view of the airfilter housing in FIG. 1, and

FIG. 3 discloses a part of FIG. 2 in an enlarged scale.

DESCRIPTION OF EMBODIMENTS

In FIG. 1, a schematic perspective view of an air filter housing 1according to a preferred embodiment of the present invention is shown.In the preferred embodiment, the housing includes two filter chambers2,3 in each of which an air filter unit F is disposed. Access to filterchambers 2,3 is gained by access openings 4,5. These access openings areclosable by doors 6,7 shown in their open position in FIG. 1.

In FIG. 2, the filter housing 1 is shown in a partially sectioned planview seen from the side of the housing 1 containing the access openings4,5. The doors 6,7 are not shown in FIG. 2. As can be seen in FIG. 2,each filter unit F comprises a circumferential wall surrounding thefilter media and ensuring that air passing through the filter unit willnot sidewise leak out of the filter unit but pass through the unit fromone end to the other, i.e. in the longitudinal direction of the filterhousing 1. In FIG. 2 the upper U and lower part L of thiscircumferential wall of a filter unit F disposed within filter chamber 2are shown. When the filter is in operation, the filter units F are heldin the filter chambers 2,3 by clamping devices 8 and 9, respectively.

Clamping device 8 consists of a frame 10 which is movable back and forthin the flow direction of the air or gas passing through the filter unitF. In the preferred embodiment shown, the means for moving the frame 10are four pneumatic cylinders 11, of which two are shown in FIG. 2. Thesepneumatic cylinders can be disposed in the corners of the rectangularframe 10 or in pairs distanced from the corners on the upper and lowerframe parts or the side parts of the frame. It is of course possible,but not preferred, to use more than four pneumatic cylinders and alsopossible to use three cylinders disposed in a triangular pattern. InFIG. 2 and in FIG. 3 which show a part of the filter housing in FIG. 2in a larger scale, the frame 10 is shown in its operative position. Inits operative position, frame 10 presses the distal end of the filterunit F, i.e. the end being distal from the frame, against a first endwall of the filter chamber 2 and is itself pressed against the proximalend of the filter unit. The filter unit F is provided with sealingelements 12, such as sealing rings or the like, affixed to the oppositeends of the circumferential wall surrounding the filter media. The frame10 is biased towards the operative position by compression springs 13acting on the piston of each cylinder 11. The sealing elements 12 oneach end of the filter unit F is somewhat compressed due to thecompressive force from the springs 13 thereby ensuring that air enteringthe filter housing can not leak out between the first end wall of thefilter chamber 2 and the distal end of the circumferential wall of afilter unit F placed in the filter chamber or between the proximal endof this wall and the frame 10. Each cylinder 11 also containsconnections (not shown) to a pressure source for moving the pistonsagainst the force of the springs 13 and thereby move the frame 10 to theright in FIGS. 2 and 3 when a filter unit F placed within the filterchamber 2 is to be discharged and replaced by a fresh filter unit.

A circumferential flange 15 is projecting inwardly from the outer wallof the filter housing 1 in the second end of the filter chamber 2. Inthe operative position of the frame 10, a portion 16 of the frame 10 isin abutment with the flange 15 via a sealing element 17. The sealingelement 17, for example an O-ring, can be affixed to flange 15 or frame10. By this arrangement it is ensured that air or gas that have passedthrough the filter unit F placed within the filter chamber 2 can notenter the space outside the circumferential wall of the filter unit,i.e. the space to the left of flange 15 in FIG. 3 or the space betweenthe first end wall of the filter chamber and the flange 15 in FIG. 2.This space contains the access opening 4 to the filter chamber. Therebyit is ensured that no contaminated air or decontamination gas will leakout of the access opening during operation of the filter or thereaftereven if the sealing of the access opening is not tight. A doublesecurity is thus obtained.

In order to be able to push a filter unit F towards the end wall of thefilter chamber 2, i.e. to the left in FIGS. 1-3, the frame 10 has afirst tubular part 18 having an outer circumference smaller than aninner circumference of the circumferential flange 15 and a secondtubular part 16 having an outer circumference larger than the innercircumference of the circumferential flange 15, the second tubular parthaving a smaller longitudinal extension than the first tubular part 18and being disposed in the portion of the frame 10 being proximal to thepneumatic cylinders 11. Thereby, the part 18 can be moved in thelongitudinal direction without being obstructed by the flange 15. Thewidth of the second tubular part 16 is chosen such as the O-ring 17 iscompressed when the frame 10 is in operative position pressing thefilter unit F against the first end wall of the filter chamber 2.

The second filter chamber 3 is constructed the same way as filterchamber 2 and includes also a clamping device similar to the clampingdevice 10,11 described above.

The filter housing of the present invention also comprises means forguiding a filter unit in the filter chamber. As best seen in FIGS. 2 and3, the filter chamber is provided with an upper rail 19 and a lower rail20 which are extended in a transverse direction relative the air flow inthe filter unit F, i.e. perpendicular to the plane of the access opening4. It is to be noted that the terms “upper” and “lower” relates to ahorizontal location of the filter housing as disclosed in the Figures,i.e. the air flow through the filter unit being horizontal. However, theair filter housing shown can instead be disposed in a vertical position,i.e. with a vertical flow of air through the filter unit, whereby therails 19 and 20 then will be disposed in opposite side walls of thefilter chamber. The rails 19,20 are in each end portion attached to asleeve 21 which in turn is slidably supported by a rod 22 extending inthe longitudinal direction and affixed in one end to the flange 15 andin the other end to an end wall in the inlet end of the filter chamber2. A compression spring 23 is disposed between said sleeve 21 and theend wall in the inlet end of the filter chamber 2 and urge the sleeveand thereby the respective rail 19, 20 to move to the right in FIGS. 2and 3. A stop element 24 is affixed to the rod 22 in order to preventthe spring 23 from moving the sleeve 21 to the right thereof. Filterunits F to be placed within filter chambers 2 and 3 are on opposite sidewalls provided with bars B or the like which are slidable in the rails19,20. When the respective sleeve 21 holding the rails 19, 20 are urgedagainst the stop element 24, the rails will be disposed in the middle ofthe filter chamber in a longitudinal direction.

The rods 22 are preferably rectangular in cross-section but other shapesis of course possible, such as circular. They can consist of solidmaterial but are preferably tubular. In the shown embodiment, the rods22 are extended from an end wall of the filter chamber to the flange 15but the rods need not reach longer than to the stop element 24, the endof the rod then functioning as a stop element. The rails 19,20 are inthe preferred embodiment simple U-girders but any type of guide rail canof course be used. In the shown example only one rail is arranged oneach of the opposite side walls but two or more rails can of course beused. However, one rail is preferred in order to facilitate introductionof a fresh filter unit F into the filter chamber.

The guide means for a filter unit function in the following way. When aused filter is to be discharged and substituted by a fresh one, thepneumatic cylinders 11 of the clamping device 8 are activated and theframe 10 will be moved out of its operative position, i.e. to the rightin the Figures, against the force of the springs 13 of the clampingdevice. Thereby the springs 23 of the guide means are free to urge therails 19,20 and thereby the used filter unit F to the right in theFigures until the sleeves 21 abut the stop elements 24. the filter unitwill then be disposed longitudinally in the middle of the filter chamber2 and its sealing elements 12 will be out of contact with both the frame10 and the end wall in the inlet end of chamber 2. The used filter unitF is now easy to take out of the filter chamber through the accessopening 4. By the co-operation between the bars B and the rails 19,20 itis ensured that the filter unit F will move in a direction perpendicularto the plane of the access opening 4.

After the used filter unit F has been removed, a fresh filter unit F isto be introduced into the filter chamber 2. This is done by placing theend of the bars B of the fresh filter unit F in the respective rail19,20 and then pushing the fresh filter unit F into the filter chamber2. Due to co-operation between the bars B and the rails 19,20 the freshfilter unit F will, guided by the rails, move in a path perpendicular toa plane through the access opening 4. In order to ascertain that therails 19,20 will be held in a longitudinally middle position by thesprings 23 even if the filter housing should be placed in a verticalposition, the force of these springs shall preferably be stronger thanthe gravitational force of the filter unit F. The ends of the bars Bcould be bevelled in order to further facilitate introduction of afilter unit into the filter chamber. Furthermore, the ends of the rails19,20 opposite to the access opening 4 can have stop elements stoppingthe movements of bars B and thereby the air filter unit F before itreaches the side wall of the filter chamber opposite to the side wallcontaining the access opening.

When the fresh air filter unit F has been placed in the middle of thefilter chamber, the pneumatic cylinders 11 are de-activated. The springs13 will then move the pistons of the cylinders 11 and thereby the frame10 to the left in the Figures. The frame 10 will in turn move the airfilter unit F to the left in the Figures until it abut the end wall ofthe filter chamber in the inlet end thereof. The filter unit F will moveonly in a strict longitudinal direction due to the positive guiding ofthe sleeves 21 on the rods 22.

The force of the springs 13 of the clamping device is much stronger thanthe force of springs 23 of the guiding device in order to ensure asuitable compression of the sealing elements 12 of the filter unit F inthe operative position of thereof.

Instead of arranging springs 23 to perform the return movement of thefilter unit from an operative position to a discharge position, thismovement could be coupled to the movement of the frame 10. A flexibleelongate element having a length corresponding to the distance betweenthe bar B and the frame 10 when the frame is brought to inoperativeposition by the pneumatic cylinders 11 of the clamping device could beattached by its ends to the frame and the bar, respectively. When theframe is brought to operative position such a flexible element has tobend a little in order to allow compression of the sealing elements onthe air filter unit by the clamping device. Such a coupling to the framewill also function if the housing is placed in a vertical position.

The described embodiments can of course be modified by skilled men inseveral ways within the scope of the present invention. For example, therails can be supported by more than the described two rods, i.e. by oneor more rods between the described rods disposed in the end portion ofthe rails. The rails can have friction-reducing linings or the like orother friction-reducing means.

1. An air filter housing (1) comprising: at least one filter chamber(2,3) with an inlet end and an outlet end for air passing through afilter unit (F) disposed in said filter chamber; an access opening (4,5)arranged in a sidewall of said filter chamber for the introduction of anair filter unit into and removal thereof out of said filter chamber; aclamping device (8) for pressing an air filter unit disposed in thefilter chamber against an end wall of said filter chamber in the inletend thereof; and a guide (19,20,21-24) for guiding an air filter unit(F) during introduction into and removal out of said filter chamber (2),wherein said guide (19,20,21-24) guides the movement of the air filterunit (F) within a filter chamber (2), wherein said guide (19,20,21-24)holds an air filter unit (F) distanced from the end walls of said filterchamber (2) during introduction into and removal out of said filterchamber, wherein said guide (19,20,21-24) include a rail (19,20) in twoopposite walls of said filter chamber, said rails being extended in atransverse direction relative to the flow direction of the air in thefilter housing and to a plane through the access opening (4) to thefilter chamber, wherein said rails (19,20) are movable in the flowdirection of the air in the filter housing.
 2. The air filter unit (F)adapted to be used in an air filter housing (1) according to claim 1,further comprising: means (B) for co-operation with guide means in theair filter housing.
 3. The air filter housing (1) according to claim 1,wherein said rails (19,20) are biased to a first position by a springforce being stronger than the gravitational force of an air filter unit(F) being guided and held in the rails, said air filter unit beingdistanced from the end walls of said filter chamber (2) in said firstposition of said rails.
 4. The air filter unit (F) adapted to be used inan air filter housing (1) according to claim 3, further comprising:means (B) for co-operation with guide means in the air filter housing.5. The air filter housing according to claim 1, wherein the flowdirection of the air in the housing is vertical and the rails are heldin a first position by a flexible element affixed to the clampingdevice, said air filter unit being distanced from the end walls of saidfilter chamber in said first position of said rails.
 6. The air filterunit (F) adapted to be used in an air filter housing (1) according toclaim 5, further comprising: means (B) for co-operation with guide meansin the air filter housing.
 7. The air filter unit (F) adapted to be usedin an air filter housing (1) according to claim 1, further comprising:bars (B) for co-operation with guide means in the air filter housing. 8.The air filter unit (F) according to claim 7, wherein said bars (B) areon the outside of opposite side walls slidable in rails (19,20) in sidewalls in said air filter housing (1).
 9. The air filter unit (F)according to claim 8, wherein the ends of said bars (B) are bevelled.